Cardiac repolarization abnormalities, often leading to life-threatening arrhythmias, represent one of the most important types of drug toxicity. Drugs that cause clinical arrhythmias are often associated with prolongation of the measured QT interval on the electrocardiogram (EKG) but this can vary from beat to beat. The majority of the drugs that result in clinical problems exhibit IKr blocking activity, but in vitro IKr inhibition is of limited predictive value. There is accumulating evidence that the lack of predictive utility of current assays reflects a failure to capture the true complexity both of drug effects (which may involve multiple targets) and the underlying substrate. We have developed a model of drug-induced repolarization abnormalities in the larval fish in order to characterize the fundamental biology of these toxic drug responses. Using heart rate (HR) response, we have established an excellent correlation with known adult human repolarization cardiac toxicity and recapitulated clinically relevant, drug-drug interactions. We now propose to extend this preliminary work, exploiting tools for genetic manipulation of the zebrafish to create a panel of 'reporter' fish modeling repolarization reserve and several proarrhythmic human disease states. We will use these reporter fish to generate a profile of repolarization responses for cardiotoxic and non-cardiotoxic drugs in order to identify features predictive of human proarrhythmia.
Specific aims are as follows; I. The generation of sensitized reporter zebrafish modeling multiple aspects of repolarization and human disease states. i) Initial cloning and characterization of zebrafish orthologs of the target genes ii) Morpholino knockdown in larval zebrafish iii) Assembly of existing mutants and generation of specific transgenic reporter lines II. Detailed characterization of the repolarization effects of a derivation set of cardiotoxic and noncardiotoxic drugs in a panel of reporter fish, i) Measurement of calcium transients in larval zebrafish hearts ii) Optical mapping of action potential duration in larval and adult zebrafish hearts III Validation of an essential predictive combination of reporter fish and repolarization parameters in a blinded, second drug set.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21GM075946-03
Application #
7270599
Study Section
Special Emphasis Panel (ZGM1-PPBC-0 (TX))
Program Officer
Okita, Richard T
Project Start
2005-09-23
Project End
2009-07-31
Budget Start
2007-08-01
Budget End
2008-07-31
Support Year
3
Fiscal Year
2007
Total Cost
$392,547
Indirect Cost
Name
Massachusetts General Hospital
Department
Type
DUNS #
073130411
City
Boston
State
MA
Country
United States
Zip Code
02199
MacRae, Calum A; Peterson, Randall T (2015) Zebrafish as tools for drug discovery. Nat Rev Drug Discov 14:721-31
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Kapur, Sunil; Macrae, Calum A (2013) The developmental basis of adult arrhythmia: atrial fibrillation as a paradigm. Front Physiol 4:221
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Deo, Rahul C; MacRae, Calum A (2011) The zebrafish: scalable in vivo modeling for systems biology. Wiley Interdiscip Rev Syst Biol Med 3:335-46
Kikuchi, Kazu; Holdway, Jennifer E; Werdich, Andreas A et al. (2010) Primary contribution to zebrafish heart regeneration by gata4(+) cardiomyocytes. Nature 464:601-5
Macrae, Calum A (2010) Cardiac Arrhythmia: In vivo screening in the zebrafish to overcome complexity in drug discovery. Expert Opin Drug Discov 5:619-632
Panáková, Daniela; Werdich, Andreas A; Macrae, Calum A (2010) Wnt11 patterns a myocardial electrical gradient through regulation of the L-type Ca(2+) channel. Nature 466:874-8
MacRae, Calum A (2010) Utility of Genetic Testing in Long QT Syndrome. Circulation 121:e440
Shin, Jordan T; Pomerantsev, Eugene V; Mably, John D et al. (2010) High-resolution cardiovascular function confirms functional orthology of myocardial contractility pathways in zebrafish. Physiol Genomics 42:300-9

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